Cyclic activity of the H_2O maser emission towards NGC 2071

摘要

A catalog of maser spectra in the 1.35-cm water-vapor line towards the maser source NGC 2071 in a region of massive star formation is presented for 1994-2010. The observations were carried out using the 22-m antenna of the Pushchino Radio Astronomy Observatory with a spectral resolution of 0.101 km/s (0.0822 km/s after the end of 2005). Based on the data throughout the monitoring since 1980, two very different cycles of maser activity were found. The first (1980-1992) is characterized by high activity within a broad range of radial velocities. Emission at velocities near 7 km/s predominated in 1980-1986, and emission near 14-16 km/s, in 1987-1992. In 1997-2008, the maser intensity was appreciably lower than in the first activity cycle. Numerous flares of individual emission features were observed. Identifications based on VLA data show that strong flares took place in both maser sources, IRS1 and IRS3. Both sources demonstrated a low level of maser activity during essentially the same epochs (1977, 1995-1997, and the close of 2009 through the beginning of 2010), although the sources are separated by at least 2000 AU.